1. Field of the Invention
Auscultation consists in listening to sounds from an organism, in particular heart and lungs, with a stethoscope. The invention relates to an application server for reducing ambiance noise in an auscultation signal, and for recording comments while auscultating a patient with an electronic stethoscope.
2. Description of the Prior Art
There exist electronic stethoscopes of the type comprising a microphone, electronic sound processing means, and sound reproducing means, such as a loudspeaker or headphones. An electronic stethoscope gives the possibility of active amplification and filtering to any desired degree. The output of an electronic stethoscope can be linked to a personal computer or a personal digital assistant for analyzing and displaying waveforms, for instance a phonocardiogram. It can be linked to a recoding device for recording the auscultation sounds.
The major drawback with these electronic stethoscopes is that ambiance noise is also captured and amplified. The auscultation of a patient can be hampered by ambiance noise, such as cries of the patient if he/she is a baby, patient's speech, or doctor's speech. In particular, if the practitioner dictates comments for the patient's file while auscultating, the ambiance sounds are superimposed onto the auscultation sounds. Thus noise can trouble the useful sounds. It may prevent the practitioner from detecting elements that are significant on a clinical basis.
It is therefore essential to clean the auscultation sound, by canceling ambiance noise. The document US2004037429 describes an electronic stethoscope for use in an environment having a high ambiance noise level, comprising:                a) a first microphone operative to be positioned against the person for generating a signal indicative at least one sound emanating from within the person and the ambiance noise of the environment;        b) at least one second microphone operative to produce a signal indicative of the ambiance noise of the environment; and        c) an ambiance noise cancellation device operatively coupled to said at least one second microphone and said headphones, said active noise cancellation system being operative to generate a signal substantially out of phase with a portion of said signal generated by said diaphragm microphone corresponding to said ambiance noise of the environment; and        d) a headphone set operative to receive and audibly transmit said signals received from said diaphragm microphone and said ambiance noise cancellation device.        
The ambiance noise cancellation device generates a signal that is approximately 180 degrees out of phase with said portion of said signal generated from said first microphone corresponding to the ambiance noise of the environment. A processor unit executes a spectral subtraction algorithm, to generate said signal being approximately 180 degrees out of phase.
The document US 2003/0002685 describes an electronic stethoscope that comprises a radio transmitter-receiver that enables to link it to a local area network comprising a server that comprises means for receiving samples of a raw auscultation signal representing auscultation sounds mixed with ambiance sounds, and sound signal processing means that can emphasize non nominal components of the auscultation signals. A processed auscultation signal is sent back to the stethoscope, up to the ears of the practitioner. It can also be recorded for medical record keeping.
A peculiar type of ambiance noise is constituted by practitioner's comments. Classically the practitioner holds a portable dictating machine in one hand and the chest piece of the stethoscope in the other hand, for recording such comments during the auscultation. These comments are later typed on a computer by a secretary, and the text file can be stored into a patient file data base.
However, it is not convenient to hold a portable dictating machine in one hand and the chest piece of a stethoscope in the other hand. In addition, dictating comments during auscultation creates an ambiance noise that is detrimental to the auscultation sounds, in particular if the auscultation signal must be recorded in the patient's medical file.
A known ambiance noise reduction device can reduce the sounds of the practitioner's comments as well as the other ambiance noises, but it does not suppress the inconvenience of holding a dictating machine in one hand, and the chest piece of the stethoscope in the other hand. A second drawback is the need of typing the dictated comments.
So, in addition to reducing the ambiance sounds in the auscultation signal, it is desirable to provide a more convenient way of recording comments into a patient file database.
This can be provided by the application server according to the invention.